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A029851 Number of self-converse semigroups of order n. 7

%I

%S 1,1,3,12,64,405,3312,44370,2209839,623492664

%N Number of self-converse semigroups of order n.

%H Andreas Distler, <a href="http://hdl.handle.net/10023/945">Classification and Enumeration of Finite Semigroups</a>, A Thesis Submitted for the Degree of PhD, University of St Andrews (2010).

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Semigroup.html">SemiGroup.</a>

%H <a href="/index/Se#semigroups">Index entries for sequences related to semigroups</a>

%F a(n)=A001423(n)*2-A027851(n).

%Y Cf. A001426.

%K nonn,hard,more,nice

%O 0,3

%A _Christian G. Bower_, Jan 27 1998. Updated Feb 19 2001

%E a(8) and a(9) from _Andreas Distler_, Jan 17 2011

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Last modified June 1 04:57 EDT 2020. Contains 334758 sequences. (Running on oeis4.)